Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $116.50   8.474%   $126.3722   $126.37   $126.35   $126.40  
  Purchase #2 $215.99   9.125%   $235.6991   $235.70   $235.70   $235.70  
  Purchase #3 $11.28   12.831%   $12.7273   $12.73   $12.75   $12.70  
  Purchase #4 $62.89   11.609%   $70.1909   $70.19   $70.20   $70.20  
  Purchase #5 $10.67   11.293%   $11.875   $11.88   $11.90   $11.90  
  Purchase #6 $218.41   3.618%   $226.3121   $226.31   $226.30   $226.30  
  Purchase #7 $157.44   3.312%   $162.6544   $162.65   $162.65   $162.70  
  7 purchase totals = $793.18       $845.8310   $845.83   $845.85   $845.90